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Resistance spot welding (RSW) is considered as predominant welding technique that is used in the manufacturing of modern automobile structure. The automobile structure is made of high strength steel which is preferred by the car industry companies due to its high strength-weight ratio. This work presents an optimization method for RSW of high-strength low-alloy steel DOCOL 500 LA. Tensile test and microstructure analysis for base material (BM) were carried out to get the mechanical properties of BM and to specify the rolling direction. Taguchi method, high efficiency technique, was applied using Minitab19 software to achieve the optimization process. Tensile shear test was carried out to evaluate the strength of welding nugget, absorbed energy and failure mode. The results showed that the optimum parameters were 8,800 A for the current, 30 cycles for the welding time and 2,230 N for the electrode force and two types of failure modes could be observed which were interfacial and full pullout mode.

This study aims to achieve in situ-formed pure Ti and Ti6Al4V coatings on 316L stainless steel through hot pressing and examine their wear and corrosion properties thoroughly in two simulated body fluids: physiological serum (0.9% NaCl) and Hanks' solution. The sintering and diffusion bonding process was conducted at 1050 °C under a uniaxial pressure of 40 MPa for 30 min in a vacuum environment of 10−4 mbar. Following sintering, in situ-formed pure Ti and Ti6Al4V coatings, approximately 1000 µm thick, were produced on 316L substrates approximately 3000 µm in thickness. The mean hardness of 316L substrates, pure Ti, and Ti6Al4V coatings are around 165 HV, 170 HV, and 420 HV, respectively. The interface of the stainless steel substrate and the pure Ti and Ti6Al4V coatings exhibited no microstructural defects, while the interface exhibited significantly higher hardness values (ranging from 600 to 700 HV). The coatings improved corrosion resistance in both electrolytes compared to the 316L substrate. Wet wear tests revealed reduced friction coefficients in 0.9% NaCl relative to Hanks' solution, highlighting the chemical interactions between the material surface and the electrolyte type and the significance of tribocorrosion in biocoatings. [ABSTRACT FROM AUTHOR]

This study aimed to develop an alternative surface hardening technique for low-carbon steel alloy type 20Ch using plasma electrolytic oxidation (PEO). The surface hardening of 20Ch alloy steel samples was achieved through PEO in a Na2CO3 electrolyte solution. Optimal processing parameters were determined experimentally by measuring voltage and applied current. Quenching was performed in the electrolyte stream, and plasma was ionised through excitation. A mathematical model based on thermal conductivity equations and regression analysis was developed to relate the key parameters of the hardening process. The results from both the experimental and mathematical models demonstrated that PEO significantly reduces hardening time compared to traditional methods. The microstructural images revealed the transformation of the coarse-grained pearlite–ferrite structure into quenched martensite. Vickers microhardness tests indicated a substantial increase in surface hardness after PEO treatment, compared to the untreated samples. The major advantages of PEO include lower energy consumption, high quenching rates, and the ability to perform localised surface treatments. These benefits contribute to overall cost reduction, making PEO a promising surface hardening method for various industrial applications. [ABSTRACT FROM AUTHOR]

This study addresses the challenge of accurately predicting corrosion rates and estimating the remaining life of underground gas pipelines, which is complicated by the complex interaction of physical factors and environmental conditions. Traditional models are inadequate in capturing these variables, leading to less reliable predictions, which this study aims to address by developing a more accurate and optimized artificial neural network (ANN) model. This study focuses on predicting corrosion rates and estimating the remaining life of underground gas pipelines using ANNs implemented in MATLAB. It incorporates both physical factors, such as maximum corrosion depth and pipe thickness, and environmental variables such as moisture, soil resistivity, and chloride concentration. The analysis identified corrosion depth and wall thickness as significant contributors, influencing material integrity by 20% and 16%, respectively. The optimal ANN model, with a Levenberg-Marquardt structure and one hidden layer of 10 neurons, achieved superior accuracy, with an MSE of 0.038 and R² of 0.9998. The study addresses the challenge of accurately predicting corrosion rates and remaining life in underground gas pipelines by developing an optimised ANN model. Its contribution lies in creating a highly accurate prediction tool that outperforms traditional models and enables more informed decisions for pipeline maintenance and safety. [ABSTRACT FROM AUTHOR]

This research aims to investigate the effect of the exfoliation corrosion exposure time on the mechanical properties, the strength and elongation, of friction stir welded Al–Li alloy type 2195-T8. The exfoliation corrosion test was performed using the exfoliation corrosion (EXCO) solution, based on ASTM G34. The samples were exposed to different exposure times 24, 48, 96, 192 and 384 h. The results showed that both the strength and elongation of the welded specimens—exposed to the exfoliation corrosion tests—were reduced. For example, the samples that were exposed to 384 h, their initial tensile strength and elongation were reduced by 13% and 17% respectively. The degradation process due to the exfoliation corrosion on the tensile strength was divided into three stages: fast (0–96 h: 443.7 MPa-416.3 MPa, the degraded rate was 0.29 MPa/h), steady (96–192 h: 416.3 MPa-413.4 MPa, the degraded rate was 0.03 MPa h ^−1 ) and medium rate (192–384 h: 413.4 MPa-386.7 MPa, the degraded rate was 0.14 MPa h ^−1 ). For the elongation, in general, the reduction was similar to the style of strength, but with different rates. The TEM images showed that this degradation was due to the dissolution of T _1 (Al _2 CuLi) and S′ (Al _2 CuMg) phase. Also, the corrosion products and their role of adherence on the surface of the tested specimens were investigated. An empirical equation p -t (mechanical properties-exposure time) was established to calculate the effect of exposure corrosion time on the performance of welded specimens.

This study aims to investigate the effect of the processing parameters in plasma electrolytic oxidation (PEO) on the corrosion resistance of magnesium alloy type AZ91. The PEO coatings were prepared on the samples using alkaline‐based electrolyte. Both unipolar and bipolar, different frequencies and duty cycles were applied. Corrosion tests, using potentiodynamic polarization, linear and cyclic, and electrochemical impedance spectroscopy techniques, were applied on the as‐received and PEO coated samples. Scanning electron microscopy was used to investigate the surface morphology, for example, micropores, as well as to measure the thickness of the coated layer by changing the processing parameters. The results show that the size of micropores is interrelated to the duty cycle percentage and current polarities, as the higher frequency causes thinner coating layers, with fewer micropores, consequently higher corrosion resistance. In addition, increasing the duty cycle, a denser and more compact coating was obtained. The XRD results showed a missing peak of the α‐Mg phase in a PEO coated sample using bipolar, the highest frequency (1666 Hz), and the highest duty cycle (66.6%). The mils per year calculations showed that the PEO coated has a lower corrosion rate by at least 8 times than the as‐received alloy. [ABSTRACT FROM AUTHOR]